The same clock is used for all cpus so we must notify the frequency change
for each one in order to update the configuration of all twd clockevents.

change since V1:
* use policy->cpus instead of cpu_online_mask
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NDave Jones <davej@redhat.com>